The present invention concerns improvements to a display device, more particularly of the liquid crystal display type, used in transmission mode and back-lit by a lighting system supplying collimated light.
Liquid crystal displays have the drawback that their electro-optical characteristics are heavily dependent on the angle of observation. Thus, in the case of very large viewing angles, a degradation in contrast and an inversion of the grey scale is observed. To remedy these drawbacks, it has been proposed that a collimated light source be used, a means for distributing the light angularly (notably a network of micro-lenses or a holographic diffuser) being associated with the modulator on the observation side. In this case, the light seen by an observer looking at the display at a certain angle is modulated by the liquid crystal display within a solid angle independent of the angle of observation. Furthermore, the use of collimated light allows various improvements to be made with regard to the display device itself and the elements associated with it to produce the complete direct-vision system.